A generator and a motor are essentially the same device mechanically. The term applied to a particular device depends on whether (i) electricity is input into the device to cause rotation of an armature (a motor) or (ii) energy is produced by the device by spinning an armature by an input torque (a generator). Generators (both DC and AC) use magnets to transform mechanical energy into electrical energy via magnetic induction. Generators have a main magnetic field, which can be produced by a permanent magnet or by a coil called a field winding located in the stator or the rotor. Conductors make up the armature winding (coil) which is usually on the rotor. When the rotor rotates the conductors cut or pass through the field. The moving of the conductors through the magnetic field causes induction to take place and a voltage to be generated in the coil. Each end of this coil can, for example, be connected to a metal band called a slip ring. Small brushes made up of carbon on metal pick up the voltage off the rings and transport it to the generator's terminals. DC generators are sometimes referred to as dynamos.
Many different type of energy have been used to rotate the armature of a generator. For example, generators have been powered by manual power, wind power, water power, and steam power (from, for example, the burning of fossil fuels). Additionally, U.S. Pat. Nos. 4,678,922 and 5,801,454 disclose air tools (for example, buffers, sanders, grinders and polishers, which include an air motor) including a generator which produces electricity from the flow of the pressurized air. The generator is integrated with the air motor of the air tool. The air tools can be provided with a light that is powered by the integral generator. The air tools can also include batteries and battery charging circuitry to store excess energy. In such air or pneumatic tools, pressurized/compressed air is typically provided from a powered compressor to the air tool solely to provide power to the air tool. The air (at a lower pressure) is then vented to the atmosphere without further use.
In a number of uses of gases, the gas is pressurized for storage in a relatively small volume (for example, in a gas cylinder as known in the art). Such container-stored gases are often used for purposes other than for storing mechanical energy in the form of a pressurized gas. For example, in a self-contained breathing apparatus (SCBA), a cylinder of compressed air is in fluid connection with a mask worn by the user. The compressed gas cylinder provides a source of breathable air/oxygen to the user of the SCBA for respiration in a hazardous environment. Similarly a self-contained underwater breathing apparatus (SCUBA) provides a source of breathable air/oxygen to a user of the SCUBA while under water.
It is common for a user of SCBA or SCUBA (or a user of a compressed gas container for other than respiration) to also use electrically powered items. For example, a firefighter equipped with a SCBA might also be equipped with a light source, a Personal Alert Safety System (PASS), and/or a thermal imaging camera such as disclosed in U.S. Pat. No. 6,486,473. As it is impractical to connect such devices to a power outlet via electrical wiring, such devices are typically equipped with batteries. The use of batteries adds extra weight and bulk to such devices. In general, the greater the power required and/or the longer the battery must provide power, the larger the battery must be and the more weight and bulk that is added to an individual (who may be already heavily laden with protective clothing and firefighting tools in the case of a firefighter).
To reduce or eliminate that above and other problems, it is desirable to develop alternative energy sources to provide electrical power.